I don't think they are in US law but in the UK they are covered by anti-cruelty laws because they are invertibrates and that is covered by that.
The Protection of Animals Acts 1911 - 2000
The first protection of Animals Act was passed in 1911. Since then there have been nine amendments to the Act. The Acts cover domestic or captive animals. This includes farm animals. The Act makes it an offence to cause any unnecessary suffering to any domestic or captive animal. It is an offence to:
cruelly beat, kick, ill-treat, over-drive, over-load, torture, infuriate, or terrify any animal;
cause unnecessary suffering through transportation;
take part in the fighting or baiting of an animal;
administer poisonous or injurious substances without good reason;
permit operations to be carried out without due care and humanity;
cause unnecessary suffering to an animal that is being destroyed to provide food for mankind; and
the coursing and hunting of a captive animal that is liberated in an injured, mutilated or exhausted condition, or the coursing and hunting of a captive animal in an enclosed space from which it has no reasonable chance of escape.
Taken from
DEFRA