と言える【といえる】

と言える means "you can say that", "it's fair to say that": you present a judgment as one the facts support, not just as your feeling. It follows a plain-form sentence; a noun or な-adjective usually takes だ before と. いえる言える is the potential form of ゆう言う.

It is at home in essays, reports and discussion, where a bare だ would sound too blunt. だろう or かもしれない after it softens the claim further.

とは言えない

The negative takes は after と: とはいえない言えない, "you can't say that". It denies the claim politely, without calling it false outright.

For a reluctant, half-hearted yes there is the double negative といえなく言えなくもない, "you could say that, I suppose".