American Assets Trust (AAT) 8-K Entry into a Material Definitive Agreement

Exhibit 5.1

750 E. PRATT STREET SUITE 900 BALTIMORE, MD 21202 T 410.244.7400 F 410.244.7742 www.Venable.com

September 17, 2024

American Assets Trust, Inc.

American Assets Trust, L.P.

3420 Carmel Mountain Road, Suite 100

San Diego, California 92121

Re: Registration Statement on Form S-3

Commission File Nos. 333-276165, 333-276165-01

Ladies and Gentlemen:

We have served as Maryland counsel to American Assets Trust, L.P., a Maryland limited partnership (the “Partnership”), and American Assets Trust, Inc., a Maryland corporation (the “Company” and, together with the Partnership, the “Note Parties”), in connection with certain matters of Maryland law relating to the offer and issuance by the Partnership of up to $525,000,000 aggregate principal amount of the Partnership’s 6.150% Senior Notes, due 2034 (the “Senior Notes”), and the guarantee by the Company of the obligations of the Partnership under the Senior Notes (the “Guarantee”). The offering and sale of the Senior Notes and the Guarantee are covered by the above-referenced Registration Statement, and all amendments thereto (the “Registration Statement”), filed by the Company with the United States Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”).

In connection with our representation of the Note Parties, and as a basis for the opinion hereinafter set forth, we have examined originals, or copies certified or otherwise identified to our satisfaction, of the following documents (hereinafter collectively referred to as the “Documents”):

1. The Registration Statement, in the form filed with the Commission under the Securities Act;

2. The Note Parties’ Prospectus, dated December 20, 2023 (the “Base Prospectus”), as supplemented by the Note Parties’ Preliminary Prospectus Supplement, dated September 10, 2024, and the Note Parties’ Prospectus Supplement, dated September 10, 2024 (together with the Base Prospectus, the “Prospectus”), each in the form in which it was filed with the Commission pursuant to Rule 424(b) promulgated under the Securities Act;

3. The charter of the Company, certified by the State Department of Assessments and Taxation of Maryland (the “SDAT”);

4. The Amended and Restated Bylaws of the Company, certified as of the date hereof by an officer of the Company;

American Assets Trust, Inc.

American Assets Trust, L.P.

September 17, 2024

Page 2

5. A certificate of the SDAT as to the good standing of the Company and the Partnership, dated as of a recent date;

6. The Certificate of Limited Partnership of the Partnership (the “Certificate”), certified by the SDAT;

7. The Amended and Restated Agreement of Limited Partnership of the Partnership, dated January 19, 2011 (the “Partnership Agreement”), among the Company, as general partner, and the persons from time to time party thereto as limited partners, certified as of the date hereof by an officer of the Company;

8. Resolutions (the “Resolutions”) adopted by the Board of Directors of the Company and a duly-authorized committee thereof, relating to, among other matters, (a) the registration and issuance of the Senior Notes and the Guarantee, (b) the Underwriting Agreement and (c) the Indenture (each as defined herein), certified as of the date hereof by an officer of the Company;

9. The Underwriting Agreement, dated September 10, 2024 (the “Underwriting Agreement”), by and among the Note Parties and Wells Fargo Securities, LLC, Mizuho Securities USA LLC and PNC Capital Markets LLC, as representatives of the Underwriters listed on Schedule I thereto.

10. The Indenture, dated as of January 26, 2021 (the “Base Indenture”), among the Company, the Partnership and U.S. Bank Trust Company, National Association, as trustee (the “Trustee”), among the Company, the Partnership and the Trustee, as amended by the officers’ certificate, dated as of the date hereof, establishing the form and terms of the Securities pursuant to the Base Indenture (the “Officers’ Certificate” and together with the Base Indenture, the “Indenture”);

11. The Global Notes evidencing the Senior Notes, dated as of the date hereof (the “Global Notes”), made by the Partnership;

12. A certificate executed by an officer of the Company, dated as of the date hereof; and

13. Such other documents and matters as we have deemed necessary or appropriate to express the opinion set forth below, subject to the assumptions, limitations and qualifications stated herein.

American Assets Trust, Inc.

American Assets Trust, L.P.

September 17, 2024

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In expressing the opinion set forth below, we have assumed the following:

1. Each individual executing any of the Documents, whether on behalf of such individual or another person, is legally competent to do so.

2. Each individual executing any of the Documents on behalf of a party (other than the Note Parties) is duly authorized to do so.

3. Each of the parties (other than the Note Parties) executing any of the Documents has duly and validly executed and delivered each of the Documents to which such party is a signatory, and such party’s obligations set forth therein are legal, valid and binding and are enforceable in accordance with all stated terms.

4. All Documents submitted to us as originals are authentic. The form and content of all Documents submitted to us as unexecuted drafts do not differ in any respect relevant to this opinion from the form and content of such Documents as executed and delivered. All Documents submitted to us as certified or photostatic copies conform to the original documents. All signatures on all Documents are genuine. All public records reviewed or relied upon by us or on our behalf are true and complete. All representations, warranties, statements and information contained in the Documents are true and complete. There has been no oral or written modification of or amendment to any of the Documents, and there has been no waiver of any provision of any of the Documents, by action or omission of the parties or otherwise.

Based upon the foregoing, and subject to the assumptions, limitations and qualifications stated herein, it is our opinion that:

1. The Company is a corporation duly incorporated and validly existing under and by virtue of the laws of the State of Maryland and is in good standing with the SDAT.

2. The Partnership is a limited partnership duly formed and validly existing under and by virtue of the laws of the State of Maryland and is in good standing with the SDAT.

3. The execution and delivery of the Indenture and the Global Notes by the Company and the Partnership, as applicable, have been duly authorized, and the Indenture and the Global Notes have been duly executed and delivered by the Company and the Partnership, as applicable.

4. The issuance of the Senior Notes and the Guarantee by the Partnership and the Company, respectively, have been duly authorized.

American Assets Trust, Inc.

American Assets Trust, L.P.

September 17, 2024

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The foregoing opinion is limited to the laws of the State of Maryland and we do not express any opinion herein concerning United States federal law or the laws of any other jurisdiction. We express no opinion as to the applicability or effect of any federal or state securities laws, including the securities laws of the State of Maryland, or as to federal or state laws regarding fraudulent transfers. To the extent that any matter as to which our opinion is expressed herein would be governed by the laws of any jurisdiction other than the State of Maryland, we do not express any opinion on such matter.

The opinion expressed herein is limited to the matters specifically set forth herein and no other opinion shall be inferred beyond the matters expressly stated. We assume no obligation to supplement this opinion if any applicable law changes after the date hereof or if we become aware of any fact that might change the opinion expressed herein after the date hereof.

This opinion is being furnished to you for submission to the Commission as an exhibit to the Company’s and the Partnership’s Current Report on Form 8-K relating to the issuance of the Senior Notes (the “Current Report”). We hereby consent to the filing of this opinion as an exhibit to the Current Report and to the use of the name of our firm therein. In giving this consent, we do not admit that we are within the category of persons whose consent is required by Section 7 of the Securities Act.

Very truly yours,

/s/ Venable LLP