Synthesizing h2 from methane is also done by electrolysis, it's just cheaper to electrolyze methane than water. This is fundamental - it takes less energy to release hydrogen from methane than from water, to such a degree that even though water is free it's still not economical. If you are concerned about people using fossil instead of synthetic methane to cut costs, you should be concerned about people using methane instead of water to cut costs. Either you can get people to comply with regulations or you can't.