Wiktionary
vb. (context idiomatic English) To be disadvantageous to someone.
Usage examples of "weigh against".
The testimony of the writer weighs in their favor in one scale, and their not being against the laws of nature does not weigh against them.
When I shall stand before God, I shall have one thing to say, to weigh against the rest.
Had the passage accidentally met our eye, we should have imagined it had fallen from the author's pen under some momentary view, not sufficiently developed to found a conjecture what he meant: and we may certainly affirm that a fragment like this cannot weigh against the authority of all other writers, against the uniform &.
For in To-gai, their warriors would find other pressing duties, and with the pressure off the Chezru Chieftain to come to resolution, attrition would weigh against them, and not for them.
At least they had their swords, but they still didn't have the proper shields to go with them, and without the shield wall, the superior individual training of the Pasule forces would weigh against the humans.
They had that information to weigh against its exit behavior and its acceleration away from Mariner, when Champlain knew they were carefully observed.