In the UK the law does not specify the electrical details, but it does state the meeting the IET wiring regulations BS 7671 ought to achieve compliance. Yes, it appears odd to begin with but it allows for the technical standards to evolve and be interpreted without needing legal oversight.
In turn that cites various other standards specifically describing RCDs as one of several means of protection against electric shock (and fire in some cases) such as BS EN 61008-1 and BS EN 61009-1 and others.
It is common for RCDs to be of the 'AC' type that is only good on an AC leakage current, but many manufactures are moving to type A as standard (pulsed DC sensitivity, as required by many European countries) and occasionally you will see type B (true DC) or F (also HF noise).
Certainly I would not use a type AC in any setup if there was any alternative!
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A quick overview aimed at electricians and consumers can be found here:
www.beama.org.uk
Just follow the download link!