I am glad to hear that the Anchorage PD will honor ICE detainers.  This is a matter of cooperation between law enforcement agencies.  

I follow this area somewhat closely, and I am not aware of any effort or authority to require local police forces to actively enforce federal immigration law.  There is a provision at 287(g), 8 U.S.C. § 1357(g) of the Immigration and Nationality Act which allows local governments to enter into agreements with the federal government that  allow local officers to enforce the federal civil immigration provisions after receiving training.  While I favor enforcement of the immigration laws, they are quite complex and, without experience and expertise, there is real risk of mistakes by the local officers.