"useful law" is correct and usable in written English.
You can use it when referring to a law that is useful or beneficial to the public or a specific group of people. For example: "The new law provides much needed relief to local businesses and is a truly useful law."
"It's a useful law, because it makes all trials more just," Niccolo Ghedini, a member of Parliament who supported the legislation, said in an interview tonight.
"We believe we will get very useful law enforcement information through this program," the official said.
"We thought the fundamental question here is, is the Second Amendment in the 21st century still useful law," Malone told the HuffPost.
"While asset forfeiture is a useful law enforcement tool to fight crime, the current lack of oversight and training poses dangers to Americans' civil liberties".
He had gathered together an alarming collection of quotations to prove it, too: Fox complaining about the useful laws that long ago defined the secular state; Fox criticizing the lay character of public education; Fox saying he wants the schools to teach religious values, meaning Catholic values.
Mr. Kachikian seems to think that class is in session and it's his job to explain to us how he installed features in Telesleuth that would only be useful to law enforcement.
In Section 3, we use the Littlewood-Paley analysis technique to derive some linear estimates and a useful product law.
"However useful, the law has always carried great potential for danger," The New York Times said in an editorial about Megan's Law in 2008.
The devices have already proved useful for law enforcement.
"He was always so helpful and useful to law enforcement.
However, often there are early warning signs concerning these individuals that could be useful to law enforcement.
