The laws that robots follow look NOTHING like the "3 laws". You don't tell a robot in English how to behave. An abstract principle like "Do not harm a human" has to be coded per situation, and there are thousands of systems which need to have their own tailored variant.
A robotic hand has to have pressure sensors to know when to stop squeezing an object that might be human so as not to cause damage. Nowhere in those device drivers are you going to see a statement that looks remotely like "do not harm a human". You'll see something like "if pressure sensors encounter resistance equivalent to soft squishy tissue, stop contracting the actuators and release until pressure = X". No concept of human, just a focus on an attribute that a human might have.
mobile robots will have to be told how to recognize potentially human objects through patterns of sensor readings and then each dimension of action will have to have its own specialized restrictions when the sensors read those patterns, or the internal model of the outside world tracks a "human" object.
A "3 laws" style rule might as well be a very abstract function or directive which has no indication of how that would manifest on the hardware of a robot. Our robotics coding right now is at the level of assembly language directives, not high level language built-in function calls. . We're still hacking the hardware, learning how to piece things together. It's going to be a few decades before we have a declarative language to express abstract rules which can be automatically compiled down into processing sensor readings to determine executability conditions for actions.
One robot to another is just another object in the world unless the robots have been explicitly coded to either learn about each other and attempt to communicate and coordinate through that learning, or they are intentionally coded to communicate with each other through various protocols ahead of time.
Statements like the 3 laws are only understood by humans. Proving that some hacked together assembly language level robotic behavior upholds the 3 laws is non-trivial. In all likelyhood it will require specialized domain specific languages to describe robotic behavior which then get compiled down to the hardware of the robot. At the level of the DSL the laws can be verified, and a formal translation from the DSL to hardware can be verified in order to guarantee the proof. Without such an integrated system, you're relying on sub-systems which are developed independently of each other to automagically cooperate together in such a way that the abstract laws are preserved as invariants.