completely legal in a topical cream/gel/solution.
powder legal(though it is a legislative loophole--unlikely to be closed) in amounts under 5g (if sold for topical use or research{most require license for research})
It is available as an injectable- there are a couple of veterinary versions used for anesthesia for cats- injectable would be less effective as almost immediate release (though high local concentrations- for a VERY short period of time).
It couble be made into a time release injectable with the right base (however as good if not better results can be obtained with topical)..... though any increase in effectiveness , if any, would be offset by scar tissue and thickening of skin at injection(s) site(s).
peace