In the case of peace officers that are agents or officers of an SPCA, the general law referred to is Agriculture and Markets Law, Article 26. The powers of peace officers working as agents or officers of an SPCA are indicated under Section 371, 372, and 373 of that article. With regard to search warrants, though those sections imply that an SPCA officer or agent may apply for a search warrant and execute it, the powers specified in those sections appear in some respects to be inconsistent with some of the provisions of Criminal Procdure Article 690 which controls the search warrant process. It looks as though the legislature updated the CPL and Agriculture and Markets laws independently and failed to impose consistency. And though one can argue that SPCA officers have successfully applied for and executed search warrants, the concept has never authoritatively been tested in a higher court. Were a defense attorney to make a motion to suppress based on an invalid search by an SPCA agent, the outcome is uncertain -- the case might be lost.
Thus, the recommendation is: if SPCAs need to search a location and seize animals, they engage a police department in the case and have that agency apply for and execute the warrant. In addition to avoiding suppression problems, this approach also provides liability protection for the humane agency.
Note: It is advisable that all search warrants be reviewed with the District Attorneys Office before submitting them to the court. Doing this averts errors that may undermine use of any evidence obtained by the search. The need for this review is underscored by the fact that proper interpretations of the statute and its requirements involve knowledge of case law interpreting said statute.
Considering that a police officer or agency has to be designated to be involved in the process,, it is best to get the officer or agency involved at the earliest stages of the investigation.