Lasers are regulated in the US at the federal level by the FDA's radiological health program.
For a decent Railgun capable of firing a second shot, a long extension cord, a serious generator or nearby mains power supply is required.
Also depends on what you want to do:
If you want to blind prey, a few watt Laser diode device suffices in a hand held, battery powered device.
If you wan to take off the leg of a charging coyote in a few seconds, you will need many hundreds of watts. (assuming you could stay on target) This could be an expensive handheld device but would require a "Sears Diehard" on your back.
If on the other hand you just want to stop a grizzly a km away coming at you, google Rheinmetall's 50kw laser. it blasted a 1/2" steel plate 1 km away.
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.50 BMG: 1 Shot 1 THRILL!