According to the US Ninth Circuit, 42 U.S.C. §1983, and the 8th Amendment to the US Constitution, prohibiting the imposition of excessive fines, or cruel and unusual punishment, on the basis that homeless people have no choice in the matter of their homelessness.

The bases of your claims are in court decisions. Is it correct that courts are the ones who grant powers?

The powers are not granted by the courts, the Constitution is interpreted by the courts. The concept of judicial review goes back to the country's founding.