1. in a way that is not legally or officially acceptable; without proper authority or basis
Usage: legal; formal
2. in a way that is not logically sound or well-founded
Usage: formal

Examples

• The contract was invalidly signed without proper witnesses.
• The election results were invalidly certified due to procedural errors.
• His argument was invalidly constructed on false premises.
• The patent was invalidly granted because prior art existed.
• The test results were invalidly interpreted by the researcher.
• The marriage was invalidly performed by an unlicensed officiant.