The closest thing I could find to the verb [to] imply (at least in the way implied is used in this context) in my dictionary was adfirmō, -āre, -āvī, -ātum. In this case you'd want to use the passive perfect participle, adfirmātum plus the adverb nōn. As for the noun power, you have a number of options depending on what kind of power you're referring to:
- potestās, f.
- (strength) vīrēs, fpl.
- (excessive) potentia, f.
- (supreme) imperium nt.
- (divine) nūmen, nt.
- (legal) auctōritās, f.
The pairs for each participle-noun pair are as follows:
- nōn adfirmāta potestās or potestās nōn adfirmāta
- nōn adfirmātae vīrēs or vīrēs nōn adfirmātae
- nōn adfirmāta potentia or potentia nōn adfirmāta
- nōn adfirmātum imperium or imperium nōn adfirmātum
- nōn adfirmātum nūmen or nūmen nōn adfirmātum
- nōn adfirmāta auctōritās or auctōritās nōn adfirmāta
When all of these are translated literally, they come out to mean something along the lines of "[type of power] having not been stated" or "[type of power] not stated", which isn't perfect, but probably as close as you can get to the English idiom "implied power" with Latin.
Minor edit:
If the phrase “implied power” is being used to describe power of a strictly legal kind, then the word auctōritās alone would suffice, since from a pragmatic standpoint, this would would have already meant “implied [legal] power” to a Roman.