Congratulations on your new home. Chamaecyparis lawsoniana is also known as Lawson's Cypress. The variety would be Lawson's. Maybe what you are asking is if it's a particular named cultivar of Chamaecyparis lawsoniana. As far as I know there are over 100 named cultivars of Lawson's Cypress and I'm not sure even an botanist would know the differences in many of them. Some have a yellow tint, some have a blue tint and others are shades of green. The cultivar names are selected when a particular trait appears, such as height, width, color and/or form.
Sorry I can't be of more help, but the best ideas I have are to either contact the nursery/gardener that planted them, or the former owner who had them planted. If they don't know the cultivar name, they may know what year they were planted. They you could contact a local nursery and ask them which cultivars were sold that year. That may help you to narrow down the possibilites of which cultivar it might be.
This US site lists some popular cultivars planted here in the US.
You might also try a google search from France with the term:
* `Alumii' - columnar, blue foliage to 25'.
* `Columnaris' - tight columnar habit, 15 - 20'.
* `Oregon Blue' - broad, columnar, with blue foliage.
* `Pembury Blue' - conical 25' (?), best blue (?).
* `Stewartii' - conical to 30', golden yellow foliage.
* `Winston Churchill' - conical, golden yellow foliage.
Chamaecyparis lawsoniana cultivars
and see which ones are popular where you are.
Never hard prune these trees. You need to prune back to green growth. Here's some info on pruning evergreen trees.
When and how to prune an evergreen
Pruning Dos and Don'ts
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.