Is it possible to have no customs union and a soft border?

Question

I know that there have been answers to similar questions in the context of Brexit, and the consensus seems to be that it's not possible. But in the question about why the US-Canada border is soft at least in some places, the answer says that the border doesn't need to be hard, because the US and Canada simply didn't make it a priority. The answerer doesn't seem to see the lack of a customs union to be a problem at all.

Now we can be pretty sure that neither the UK nor Ireland would make a hard border a priority. On the contrary, it's very likely that it would be a priority for the both sides to avoid having a hard border even in the case of no-deal Brexit; nobody wants the return of The Troubles.

Does it mean that a soft border without a customs union is perfectly possible, but the EU simply doesn't want it, and uses its strong negotiating position to avoid such an outcome?

PS. I know that it isn't the case that the whole Canadian border is as soft as in the linked question. But the smugglers will obviously use the softest parts of the border for illegal activities, so that doesn't really change my points.

Answer 1

Just because you don't have a fence on every piece of land that separates two countries doesn't make the border soft in the sense discussed in the context of Brexit. It might make it soft in some security (or Trump) dictionary, but that's another matter.

As far as Brexit goes, a soft border has official crossings that look like in like this video; as in you're just driving on a highway and unless you pay close attention to the signs on the side of the road you'll completely miss it. (The border is actually where the striped yellow line on the side of the road becomes a continuous white line.)

A hard border (which the US-Canada one qualifies as for Brexit-discussion purposes) looks like this

Now show me a US-Canada crossing on a major highway (not some backroad) that looks like in the first picture.

What is being discussed more seriously as a model of the future Irish border is the Norway-Sweden border (the former is not in the EU, while the latter is). Here on a number of roads where trucks are banned, there is only video monitoring of the crossing. (Trucks have to use roads with regular border checks, for now.)

As a side/historical note, back when the Irish border was militarized, the British army attempted to close the back/"unapproved" roads (to all vehicles) by cratering them.

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As for the EU vision (or to be more precise that of a study commissioned by the EU Parliament) for what's feasible for the Irish border (in the absence of the backstop)... it's actually not too far from the US-Canadian or Norway-Sweden border(s), including heavy use of CCTV, remote reading of driver licenses, and pre-approval of low-risk transporters who would see simplified border procedures. As the Independent commented on the "smart border" vision outlined in that study:

Now, does all this add up to a “hard border”? The definition of “hard” is, perhaps, open to argument. But what is clear is that the “Smart Border 2.0” proposals do involve physical infrastructure and border guards. This regime would be very different from the completely open border that resulted from the Good Friday Agreement. That can only be retained if the UK concludes a wide-ranging customs union agreement with the EU.

Answer 2

As nobody actually answers....

The soft/hard at least in the Brexit context has nothing to do with how easy/difficult it would be to transfer people or goods illegally, but rather about whether one is required to do "administrative preparations, like reporting what is passed over and/or carrying passports". I have been stopped by a border controller between Germany and Austria [I crossed by car] also after the Schengen accord, but although at least officially one must carry an ID [fulfilling certain requirements, which e.g. a driving license does not fulfull] when crossing a country border within Schengen, still, in this contexts, the border e.g. between Austria and Germany is considered soft.

p.s. to @michau there are many border controls between the Schengen countries, and during the "refugee crisis" in 2015, even crossing the bridge between Malmo (Sweden) and Copenhagen (Denmark) was controlled.