SAR, medevac, fire fightings etc. are all roles that the Blackhawk is perfectly suited for and all for which it has dedicated variants.
As for law enforcement use again I don’t see a problem with it, the use of them is mostly restricted to very special cases (FBI/DEA etc) due to cost of both the aircraft itself and the operational costs.
The Mexican federal police is indeed essentially an army at this point since they engage in paramilitary operations against the cartels.
On the other hand Cobras have no use other than to spray a target with their auto cannon or missiles.
So I was really curious what police force in the US or anyone is operating attack helicopters.