Well, of course there is. The black and white of each issue can be found in scriptures; even if it isn't written as 'thou shalt not' we are responsible for knowing how God would have us live, act and witness in this world.
Take the issue of dress as an example. Modest dress is clearly pointed out as a must for women (1 Timothy 2:9), that is the black and white of the issue. The application of this in our lives does engulf some personal preference. I am the first to confess that if any pastor stood before me on Sunday morning and said that all female members would be expected to wear ankle length, loose fitted dresses that were absent from any embellishment or style - I would laugh out loud in rebellion (not a great reaction to authority but I'm just being honest!).
The leadership of a church may set a dress standard for positions of serving - like a uniform - such as men wear jackets and ties, however to pass it off as a biblical standard is untrue. For the most part, I do wear a skirt when I am simply attending church. The idea behind this practice is simply that I want to look my best when I am in God's house and I want to be ready to serve if I am needed.
Having said that, there are plenty of dresses and skirts that do not fit under the term 'modest'. Some of these are seen at church, too. So modesty is not about the type of clothing, it is really more about how and why the clothing is worn. Does the outfit bring to mind the words 'decent', 'honourable', and 'virtuous'? OR does it say 'proud', 'conceited' and 'vain', never mind bringing the term 'available' to the mind of those looking? Regardless of some of the arguments I have heard, the difference in these terms is plain. Any particular article of clothing can be worn modestly or immodestly.
So where is the line between biblical and legalistic? That line is only found in our individual reasons for the decisions we make. Are we following a dress code to please people or God? Are we jumping on an issue bandwagon without seeking God's wisdom? If the way we dress is only an opinion, or to be part of the church crowd, rather than a conviction - that makes it legalistic; it will be short lived.
This particular example of dress is one of the simpler issues to discern. Maybe one day I'll be brave enough to take the conversation further into the 'Christian liberty" discussion. For now, I'll leave the legalism argument with my black and white response: know why you do it; know why you believe it; know why God would like your answers!