An important part of a professional lawyer's job is looking for inconsistencies and loopholes. This may be preemptive, such as determining the exact wording of a contract, or it may be reactive ("You didn't actually say that it was required."). In the context of practicing law, this is both expected and laudable. Well, mostly laudable. See the case of Dickens' Jarndyce v Jarndyce https://en.wikipedia.org/wiki/Jarndyce_and_Jarndyce, which serves as a classic literary example of the process run amok.
Outside of the law, however, the same process can produce endless discussion of the most minute details and questioning of phrasing ("spec-lawyering" clearly refers to the process of making a specification over-precise or over-broad). It is this situation in which lawyering takes on a universally negative connotation.
A classic (although not legal) example of this focusing on minutiae at the expense of the larger issue is George Tyrell's line: "if the Jesuits were accused of killing three men and a dog, they would invariably produce the dog alive."