The Supreme Court heard arguments on the question
Subsequently, the lady sued the police and town. The 10th Circuit ruled that due process was violated when the police did not respond to her reports of a violation of the protective order. Apparently, from reports of the oral argument, the Court was skeptical of this finding.
Personally, I am of a belief that domestic matters are, and ought to be, State matters. However, as the reader who forwarded this to me pointed out, the Congress has recently stepped into the domestic area with the Schiavo legislation. Now, I've not done any serious reading or analysis on that case (not crimlaw) but it is clearly a huge step into a State area by Congress. Is more of the same to come in the future?
Probably. When a congressman goes home it can be hard to explain his votes on foreign aid or foreign trade matters. However, voting "aye" on the "Police Must Respond to Domestic Violence Act" is going to be something which everyone will understand. And how many are going to care that it's an expansion of federal powers?