contract-law
can government (US/UK) simply declare agreements to pay in crypto null&amp;void?
<p>I have no expertise in this, but as a layman I've been thinking about the ways in which governments can destroy the value of cryptocurrencies if they really want to do so.</p>
<p>In China, all cryptocurrency transactions are considered illegal. India has flirted with the idea of a ban, though it isn't clear whether the Indian government go ahead with such a ban.</p>
<p>If in the US/UK there were a political consensus to discourage the use of cryptocurrencies, what could the government do? Short of having a full ban (which wouldn't be popular), could they for instance make a new law saying that all agreements in which A agrees to pay B in cryptocurrencies are no longer legally binding?</p>

<h2>in general: yes</h2>
<p>The government of a country is free to ban anything the constitution of its own country does not prevent it from banning. No constitution anywhere decrees that you have a right to cryptocurrency. So any government could declare it valueless and ban its trade and possession in its country.</p>
<h2><a href="/questions/tagged/united-states" class="post-tag" title="show questions tagged &#39;united-states&#39;" aria-label="show questions tagged &#39;united-states&#39;" rel="tag" aria-labelledby="united-states-container">united-states</a></h2>
<p>While the constitution of the US bans it to prevent banning <em>all</em> arms (2nd amendment) or enacting censorship (1st amendment), nothing in the constitution establishes a right to cryptocurrency. The only amendment that would be relevant is that in banning it, there needs to be <strong>due process of law</strong> under the fourteenth amendment in depriving them of property. This can be most easily done by declaring a cutoff date after which usage and possession of cryptocurrency is made illegal.</p>
<p>But does the federal government have power? It does. Any transaction on the internet automatically is Interstate commerce, thus the <a href="https://www.law.cornell.edu/wex/commerce_clause" rel="nofollow noreferrer">commerce clause</a> applies and as a result, federal laws apply. The same paragraph vests all decisions on minting and the shape of minting with the US Congress in <a href="https://constitution.congress.gov/browse/essay/artI-S8-C5-1/ALDE_00001066/" rel="nofollow noreferrer">Art. I, S.8 c.5</a>. Most relevant:</p>
<blockquote>
<p>The Congress shall have Power ... to regulate commerce with foreign nations, and among the several states, and with the Indian tribes.</p>
</blockquote>
<p>They can ban the trade of Cryptocurrency across state lines under that clause just as much as they could have banned trading alcohol. They went for the 18th amendment instead, because that banned intra-state sales too. Since the servers where cryptocurrency is stored are usually <em>not</em> in your state, in fact not even the US usually, such transactions fall under the commerce clause and federal law.</p>
