WASHINGTON — Two federal courts here issued decisions on Friday addressing the impact of Citizens United, January’s big Supreme Court campaign finance ruling, on a new issue — whether the government may constitutionally restrict the size of contributions to groups that spend money to support political candidates.

One court said that individual contributions to advocacy groups known as 527s may not be limited. Another said that contributions to political parties can, though it said it was aware the resulting playing field might not be a level one.

Stephen M. Hoersting, a lawyer for the winning side in the first case, said the ruling represented a logical and welcome extension of Citizens United.

“The court affirmed,” Mr. Hoersting said in a statement, “that groups of passionate individuals, like billionaires — and corporations and unions after Citizens United — have the right to spend without limit to independently advocate for or against federal candidates.”