Juno is said to rule over commitment/marriage.I consider its relevance only in examining the sign and its overall relation to the theme of relationships/ marriage in the chart concerned.
Libra in the 1st is of itself a contradiction. Much like Sun in 7th, Saturn in 4th.
Barring Mars/Pluto/Sun in 1st ,you don't go after what you want directly for fear that it may upset others. So you are prone to be a populist and live your wants vicariously through others.
Juno in 1st has a Venus in 1st similar vein. It suggests that you are a desirable long-term mate. But is that what you want?
If you don't know what you want, you may fall into marriage/committment because you think it's whats acceptable and expected. So a marriage proposal may flatter u enough to jump right in.
Venus in 1st-esp in Libra/Leo, loves to be flattered by others. And can gravitate towards becoming a populist.
Juno in 1st-esp Lib/Gemini, can be flattered by many suitors for marriage. But they need to be certain about how they feel about commitment 1st and not be whisked away by the idea that a drop dead gorgeous person wants to be with them and has declared their love for the Juno person publicly
Or that the individual considers the Juno in 1st the proverbial knight/virtuous princess that they have been waiting for their whole life etc.
Juno in Lib/Pisces in 1st can fall into that trap. And Juno in Virgo/Cap in 1st can do what is right by moral standards and societal expectations