'In line with something' has a very general usage: it just means it is in general agreement or harmony with the environment. That environment could be the law, a regulatory framework, general agreement on values, worldview, 'seeing eye to eye' within a group, etc. "Our views were not in line with the others." "We reviewed our policy and found that it was not in line with our values of sustainable development." 'To comply with' or 'in compliance with' has a more legalistic meaning in relation to formal rules/laws of a system with authority. But, generally, it requires authority and an ability to compel-- i.e. police can force a person to 'comply' by virtue of their authority. "To comply with government regulations." " The company hired a new compliance officer in order to assure compliance with the new 2024 requirements."

They are quite similar. In line with is more like observing a set of protocols or guidelines. Compliance is talking more about non negotiable requirements. Hope that helps