Yes they have to use them or they can’t justify them. Without expanding the use of SWAT there just isn’t enough high risk events to justify a SWAT team in most jurisdictions.
Here is a portion of an article that I read. I had heard that cities could be held liable for not having some type of response team.
If you think a SWAT team might be good for your agency, but
you’re still on the fence, you might note that not having one can present its own problems. The failure to develop and maintain a SWAT unit, where viable, can be costly. Courts may not mandate that an agency have a SWAT team, but they can encourage its creation.
A 1982 barricade situation ended with an Anchorage patrol
officer taking a suspect’s life. The court ruled the officer’s actions justifiable, but concluded that the absence of mitigators, i.e., a SWAT unit, limited the police department’s options in resolving the situation. The city was held liable for the suspect’s death. Such was the impetus that gave rise to the Anchorage (Alaska) Police Department’s SWAT team.