Hemp protein is a industrial byproduct from hempseed where the seeds (balanced macronutrient profile) have their oil extracted into Hempseed oil, and the remainding seedmeal that is high in protein relative to the seeds is then processed into Hemp protein supplements.
Hemp that is currently on the market is a strain low in THC (the intoxicant and psychoactive agent in Marijuana) and does not confer intoxicating properties. It is usually not a pure protein supplement, as it has up to 10% fatty acids by weight (pretty balanced between omega-3 and omega-6 fatty acids and generally high in polyunsaturated fatty acids) and confers a higher inherent fiber content relative to other Protein supplements. The protein portion of hemp is not a complete protein source, due to being low in Lysine (the rate limiting essential amino acid); it is also relatively low in leucine, but is relatively high in both L-Tyrosine and Arginine.
There is a cannabinoid content in Hemp, although they are cannabinoids that do not interact with the two classical cannabinoid receptors in the human body and are unlikely to have the same neural properties attributed to marijuana. These may confer some health properties unique to hemp products (either hempseed protein or Marijuana) but in the context of using hemp protein as a meal replacement they are not studied.
Currently, hemp protein appears to be a viable meal replacement option and has the benefit of having a higher fiber content but is not yet linked to unique health benefits (or harms) to establish its importance over other dietary sources of protein.